A British man has lost his legs in a shark attack after he ignored a warning not to go swimming at a South African beach. The 42-year-old, who has not yet been named, ignored signs at the beach in Cape Town warning against entering the water.

Authorities said he was attacked by a great white shark at Fish Hoek Beach.

The attack came an hour-and-a-half after shark spotters had seen the animal and raised a warning flag.

A siren was also sounded as the beach was closed, officials said in a statement.

The man went swimming anyway and the great white struck before onlookers could pull him out.

His right leg was completely bitten off and his left leg severed below the knee, according to the National Sea Rescue Institute.

The shark responsible for the attack was caught on camera by onlookers Although the victim has not been named, the institute said he was believed to be a British national who lives in South Africa.

Video footage of the beach after the attack shows a shark in the water off the shore as a helicopter flies the man to hospital. A statement from the authorities said: "When the victim entered the water, the beach was still closed and the shark flag indicating the presence of a white shark was flying."

Three nearby beaches were also closed following the attack because the shark could still be seen in the area.

Cape Town operates a shark-spotter programme on its beaches to warn people when to leave the water.

At least three sharks had been spotted off the beach on the morning of the attack alone.